Microcapsules have been used for various applications. Normally, microcapsules are synthesized in spherical or somewhat spherical shapes. Recently, microcapsules have been used for smart coatings for corrosion applications. For instance, the pH sensitive microcapsules disclosed by Li and Calle in 2009 NACE International conference paper 09499 and 2007 NACE International conference paper 07228, and in U.S. Pat. No. 7,790,225 B1 (Luz Calle et al., issued Sep. 7, 2010) have been used for the controlled release of a corrosion indicator, or a corrosion inhibitor, or a self-healing agent when corrosion occurs. Mechanically breakable microcapsules are also used in self-healing composite disclosed by White et al. in Nature, 2001, 409:794-797.
There are few disclosures on making elongated capsules (around or above 1 mm), but not on making elongated microcapsules (below 100 microns). For instance, Aebischer et al (U.S. Pat. No. 5,418,154) prepared elongated seamless capsules containing biological materials by extruding the capsule core content and the polymeric casting solution through two concentric bores. However, there are a number of shortcomings in this approach. The size of the capsule is limited by the size of the bores, which makes it difficult to form small microcapsules, i.e., smaller than 200 microns. The scale up of the process requires additional equipment set up, the cost of mass production can be very high and even forbidden for many industries, such as the coating industry or composite applications.
Thus, there exists a need for better techniques for synthesis of elongated microcapsules for producing microcapsules about or below 200 microns, as well as suitable for scale up for industrial production.